<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
-<!--
- SPDX-License-Identifier: LGPL-2.1+
-
- This file is part of systemd.
-
- Copyright 2012 Lennart Poettering
--->
-
-<refentry id="sd_journal_query_unique">
+<refentry id="sd_journal_query_unique" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_journal_query_unique</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<refnamediv>
<refname>sd_journal_query_unique</refname>
<refname>sd_journal_enumerate_unique</refname>
+ <refname>sd_journal_enumerate_available_unique</refname>
<refname>sd_journal_restart_unique</refname>
<refname>SD_JOURNAL_FOREACH_UNIQUE</refname>
<refpurpose>Read unique data fields from the journal</refpurpose>
<paramdef>const char *<parameter>field</parameter></paramdef>
</funcprototype>
+ <funcprototype>
+ <funcdef>int <function>sd_journal_enumerate_available_unique</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>const void **<parameter>data</parameter></paramdef>
+ <paramdef>size_t *<parameter>length</parameter></paramdef>
+ </funcprototype>
+
<funcprototype>
<funcdef>int <function>sd_journal_enumerate_unique</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
<refsect1>
<title>Description</title>
- <para><function>sd_journal_query_unique()</function> queries the
- journal for all unique values the specified field can take. It
- takes two arguments: the journal to query and the field name to
- look for. Well-known field names are listed on
- <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
- Field names must be specified without a trailing '='. After this
- function has been executed successfully the field values may be
- queried using <function>sd_journal_enumerate_unique()</function>.
- Invoking this call a second time will change the field name being
- queried and reset the enumeration index to the first field value
- that matches.</para>
-
- <para><function>sd_journal_enumerate_unique()</function> may be
- used to iterate through all data fields which match the previously
- selected field name as set with
- <function>sd_journal_query_unique()</function>. On each invocation
- the next field data matching the field name is returned. The order
- of the returned data fields is not defined. It takes three
- arguments: the journal context object, plus a pair of pointers to
- pointer/size variables where the data object and its size shall be
- stored in. The returned data is in a read-only memory map and is
- only valid until the next invocation of
- <function>sd_journal_enumerate_unique()</function>. Note that the
- data returned will be prefixed with the field name and '='. Note
- that this call is subject to the data field size threshold as
- controlled by
- <function>sd_journal_set_data_threshold()</function>.</para>
+ <para><function>sd_journal_query_unique()</function> queries the journal for all unique values the
+ specified field can take. It takes two arguments: the journal to query and the field name to look
+ for. Well-known field names are listed on
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ but any field can be specified. Field names must be specified without a trailing
+ <literal>=</literal>. After this function has been executed successfully the field values may be queried
+ using <function>sd_journal_enumerate_unique()</function> and
+ <function>sd_journal_enumerate_available_unique()</function>. Invoking one of those calls will change the
+ field name being queried and reset the enumeration index to the first field value that matches.</para>
+
+ <para><function>sd_journal_enumerate_unique()</function> may be used to iterate through all data fields
+ which match the previously selected field name as set with
+ <function>sd_journal_query_unique()</function>. On each invocation the next field data matching the field
+ name is returned. The order of the returned data fields is not defined. It takes three arguments: the
+ journal object, plus a pair of pointers to pointer/size variables where the data object and its size
+ shall be stored. The returned data is in a read-only memory map and is only valid until the next
+ invocation of <function>sd_journal_enumerate_unique()</function>. Note that the data returned will be
+ prefixed with the field name and <literal>=</literal>. Note that this call is subject to the data field
+ size threshold as controlled by <function>sd_journal_set_data_threshold()</function> and only the initial
+ part of the field up to the threshold is returned. An error is returned for fields which cannot be
+ retrieved. See the error list below for details.</para>
+
+ <para><function>sd_journal_enumerate_available_unique()</function> is similar to
+ <function>sd_journal_enumerate_unique()</function>, but silently skips any fields which may be valid, but
+ are too large or not supported by current implementation.</para>
<para><function>sd_journal_restart_unique()</function> resets the
data enumeration index to the beginning of the list. The next
will return the first field data matching the field name
again.</para>
- <para>Note that the
- <function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro may be used
- as a handy wrapper around
- <function>sd_journal_restart_unique()</function> and
- <function>sd_journal_enumerate_unique()</function>.</para>
+ <para>Note that the <function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro may be used as a handy wrapper
+ around <function>sd_journal_restart_unique()</function> and
+ <function>sd_journal_enumerate_available_unique()</function>.</para>
<para>Note that these functions currently are not influenced by
matches set with <function>sd_journal_add_match()</function> but
<refsect1>
<title>Return Value</title>
- <para><function>sd_journal_query_unique()</function> returns 0 on
- success or a negative errno-style error code.
- <function>sd_journal_enumerate_unique()</function> returns a
- positive integer if the next field data has been read, 0 when no
- more fields are known, or a negative errno-style error code.
- <function>sd_journal_restart_unique()</function> returns
- nothing.</para>
+ <para><function>sd_journal_query_unique()</function> returns 0 on success or a negative errno-style error
+ code. <function>sd_journal_enumerate_unique()</function> and and
+ <function>sd_journal_query_available_unique()</function> return a positive integer if the next field data
+ has been read, 0 when no more fields remain, or a negative errno-style error code.
+ <function>sd_journal_restart_unique()</function> doesn't return anything.</para>
+
+ <refsect2>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <xi:include href="sd_journal_get_data.xml" xpointer="EINVAL"/>
+ <xi:include href="sd_journal_get_data.xml" xpointer="ECHILD"/>
+ <xi:include href="sd_journal_get_data.xml" xpointer="EADDRNOTAVAIL"/>
+ <xi:include href="sd_journal_get_data.xml" xpointer="ENOENT"/>
+ <xi:include href="sd_journal_get_data.xml" xpointer="ENOBUFS"/>
+ <xi:include href="sd_journal_get_data.xml" xpointer="E2BIG"/>
+ <xi:include href="sd_journal_get_data.xml" xpointer="EPROTONOSUPPORT"/>
+ <xi:include href="sd_journal_get_data.xml" xpointer="EBADMSG"/>
+ <xi:include href="sd_journal_get_data.xml" xpointer="EIO"/>
+ </variablelist>
+ </refsect2>
</refsect1>
<refsect1>
<title>Notes</title>
- <para>All functions listed here are thread-agnostic and only a single thread may operate
- on a given <structname>sd_journal</structname> object.</para>
+ <xi:include href="threads-aware.xml" xpointer="strict"/>
- <para>The <function>sd_journal_query_unique()</function>,
- <function>sd_journal_enumerate_unique()</function> and
- <function>sd_journal_restart_unique()</function> interfaces are
- available as a shared library, which can be compiled and linked to
- with the
- <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- file.</para>
+ <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
</refsect1>
<refsect1>
<title>Examples</title>
- <para>Use the <function>SD_JOURNAL_FOREACH_UNIQUE</function> macro
- to iterate through all values a field of the journal can take. The
- following example lists all unit names referenced in the
- journal:</para>
-
- <programlisting>#include <stdio.h>
-#include <string.h>
-#include <systemd/sd-journal.h>
-
-int main(int argc, char *argv[]) {
- sd_journal *j;
- const void *d;
- size_t l;
- int r;
-
- r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY);
- if (r < 0) {
- fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
- return 1;
- }
- r = sd_journal_query_unique(j, "_SYSTEMD_UNIT");
- if (r < 0) {
- fprintf(stderr, "Failed to query journal: %s\n", strerror(-r));
- return 1;
- }
- SD_JOURNAL_FOREACH_UNIQUE(j, d, l)
- printf("%.*s\n", (int) l, (const char*) d);
- sd_journal_close(j);
- return 0;
-}</programlisting>
+ <para>Use the <function>SD_JOURNAL_FOREACH_UNIQUE</function> macro to iterate through all values a field
+ of the journal can take (and which can be accessed on the given architecture and are not compressed with
+ an unsupported mechanism). The following example lists all unit names referenced in the journal:</para>
+ <programlisting><xi:include href="journal-iterate-unique.c" parse="text" /></programlisting>
</refsect1>
<refsect1>
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